近日，美国哈佛大学的Joost J.Vlassak课题组与麻省理工学院的Peter J.Foster等人合作，研究了活细胞骨架材料中的耗散和跨尺度能量传播。相关成果已于2023年3月31日在国际学术期刊《美国科学院院刊》上发表。

该课题组使用最新开发的皮卡瓦级量热计来实验测量表现出突现大尺度流动的活性微管凝胶的能量学。研究发现，仅约占系统总能耗的十亿分之一的能量贡献于这些突现的流动。研究人员开发了一个化学动力学模型，定量捕捉系统的总热耗散如何随着ATP和微管浓度变化而变化，但在高马达浓度下分解，表明存在马达之间的干扰。最后，他们还估算了能量损失在不同尺度上如何积累。这些结果共同强调了能量效率作为工程活性材料时的一个关键考虑因素，也是向开发生命系统非平衡热力学迈出的重要一步。

研究人员表示，生命系统本质上是非平衡的：它们利用代谢产生的化学能来推动其突现的动力学和自组织。细胞骨架是这些动力学的一个关键驱动因素，是活性物质的典型例子，其中分子马达注入的能量在长度尺度上形成级联作用，使材料突破了热力学平衡的限制，展示了仅因为不断注入能量才能出现的新型非平衡动力学。尽管近年来在使用局部探针量化熵产生和详细平衡破缺方面取得了实验进展，但人们对于活性物质的能量学以及能量如何从分子尺度传播到突现的尺度仍知之甚少。

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附：英文原文

Title: Dissipation and energy propagation across scales in an active cytoskeletal material

Author: Foster, Peter J., Bae, Jinhye, Lemma, Bezia, Zheng, Juanjuan, Ireland, William, Chandrakar, Pooja, Boros, Rémi, Dogic, Zvonimir, Needleman, Daniel J., Vlassak, Joost J.

Issue&Volume: 2023-3-31

Abstract: Living systems are intrinsically nonequilibrium: They use metabolically derived chemical energy to power their emergent dynamics and self-organization. A crucial driver of these dynamics is the cellular cytoskeleton, a defining example of an active material where the energy injected by molecular motors cascades across length scales, allowing the material to break the constraints of thermodynamic equilibrium and display emergent nonequilibrium dynamics only possible due to the constant influx of energy. Notwithstanding recent experimental advances in the use of local probes to quantify entropy production and the breaking of detailed balance, little is known about the energetics of active materials or how energy propagates from the molecular to emergent length scales. Here, we use a recently developed picowatt calorimeter to experimentally measure the energetics of an active microtubule gel that displays emergent large-scale flows. We find that only approximately one-billionth of the system’s total energy consumption contributes to these emergent flows. We develop a chemical kinetics model that quantitatively captures how the system’s total thermal dissipation varies with ATP and microtubule concentrations but that breaks down at high motor concentration, signaling an interference between motors. Finally, we estimate how energy losses accumulate across scales. Taken together, these results highlight energetic efficiency as a key consideration for the engineering of active materials and are a powerful step toward developing a nonequilibrium thermodynamics of living systems.

DOI: 10.1073/pnas.2207662120

Source: https://www.pnas.org/doi/10.1073/pnas.2207662120

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